In debt. Its antithesis, "in the black," refers to having a balanced budget.
got angry
This is not an idiom. When you see AS ___ AS ___, you are looking at A Simile. This one is comparing something to the red color of a turkey's wattle.
This is a term used when someone turns red (blushes) because they are embarrassed.
The color of the herring in the idiom "-herring" is red.
It means to be patriotic (by reference to flying the flag).
It is red tape.
Your face usually turns red when you are embarrassed, so this phrase means that someone was ashamed of something.
It can mean several things, depending on whether it is meant literally or as an idiom. Literally, it would mean that the tip of something is red-hot, or glowing with heat. As an idiom, a "tip" is information that can be used in a situation, so a "red-hot" one would be something that is especially important at the moment, something timely and greatly useful.
simile
It is not an idiom, it means your nose is itching.
It's not really an idiom. It means "what are you thinking about."
RFP is not an idiom. It's an abbreviation.